UVA1395 Slim Span(枚举最小生成树）

题意： 求最小生成树中，最大的边减去最小的边 最小值。

看了题解发现真简单=_=

将每条边进行从小到大排序，然后从最小到大一次枚举最小生成树，当构成生成树的时候，更新最小值

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int INF = 0x3f3f3f3f;
const int Max = 5000;
const int N = 110;
int father[N];
struct Edge
{
    int x, y, dist;
};
Edge edge[Max];
int cmp(Edge t1, Edge t2)
{
    return t1.dist < t2.dist;
}
int find_father(int x)
{
    if (x == father[x])
        return x;
    return father[x] = find_father(father[x]);
}
int main()
{
    int n, m;
    while (scanf("%d%d", &n, &m) != EOF)
    {
        if (m == 0 && n == 0)
            break;
        for (int i = 0; i < m; i++)
        {
            scanf("%d%d%d", &edge[i].x, &edge[i].y, &edge[i].dist);
        }
        sort(edge, edge + m, cmp);
        int minn = INF;
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j <= n; j++)
                father[j] = j;
            int cnt = 0;
            for (int j = i; j < m; j++)  // 依次枚举每一个生成树
            {
                int fx = find_father(edge[j].x);
                int fy = find_father(edge[j].y);
                if (fx != fy)
                {
                    father[fx] = fy;
                    cnt++;
                    if (cnt == n - 1) // 一旦构成生成树，j是最大边权，i是最小权，相减更新
                    {
                        minn = min(minn, edge[j].dist - edge[i].dist);
                        break;
                    }
                }
            }
        }
        if (minn == INF)
            printf("-1
");
        else
            printf("%d
", minn);
    }
    return 0;
}